Poor customer service

I settled my credit card in August 2022 in full. My account was closed and FNB removed the account from my internet banking profile. This morning I received a call from Blake and Associates informing me of an outstanding amount of R700. It is impossible to resolve the issue on any of FNB's channels. The secure chat option took me 30 minutes with no progress at all. I called my private banker and from there on it was a nightmare. I was transferred four times from the one department to the next and eventually after 13 minutes my call was cut-off. No progress. It is absolutely shocking that a bank cannot assist in solving queries. Problem still not addressed.